Heat pipe

ABSTRACT

A heat pipe includes a pipe body having two enclosed ends and defining a heat absorbing section and a condensing section, a wick structure formed on the inside wall of the pipe body and having a thickness relatively thicker at the heat absorbing section and relatively thinner at the condensing section, and a working fluid filled in the pipe body. By means of the design that the diameter of the space surrounded by the wick structure in the condensing section is greater than that in the heat absorbing section, the heat pipe eliminates fluid accumulation and maintains excellent temperature uniformity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates a heat pipe and more particularly, to aheat pipe of better temperature uniformity.

2. Description of the Related Art

A regular heat pipe generally comprises an enclosed pipe body, a wickstructure provided inside the enclosed pipe body, and a working fluidfilled in the enclosed pipe body. The heat pipe transfers heat energy bymeans of the phase change of the working fluid between liquid and gasand flowing of the working fluid in the enclosed pipe body. Duringoperation, the working fluid in the heat absorbing section of theenclosed pipe body is heated into steam, the steam thus producedimmediately disperses and is then condensed into liquid at thecondensing section of the enclosed pipe body, and the condensed liquidis then guided backwards to the heat absorbing section by means of thecapillary effect of the wick structure. This heat exchange action isrepeated again and again, achieving the desired heat transfer effect.

In some installation cases due to space limitation, for example, forinstallation in a notebook computer, display card, or any other hotsources, the heat pipe may have to be flattened. When a heat pipe isflattened, as shown in FIG. 4, the internal space of the heat pipe 70 isrelatively reduced, and therefore the steam space becomes smaller andthinner. When steam is condensed into fluid 79 in the condensing sectionC, one part of the fluid 79 is guided back to the heat absorbing sectionH while the other part of the fluid 79 is kept in the condensing sectionC. This condition occurs just because the space surrounded by the wickstructure 73 is reduced and this reduced space works as a capillary tubeto cause a capillary effect. Therefore, the aforesaid heat pipe designcannot eliminate accumulation of the fluid 79 inside the condensingsection C.

Because the fluid is not fully guided back from the condensing section Cto the heat absorbing section H, liquid gas conversion cannot beperformed in the condensing section C that has fluid accumulation, i.e.,thermal energy cannot be transferred to this location. This fluidaccumulation results in a relatively lower temperature level,obstructing temperature uniformity of the heat pipe and lowering itsheat transfer efficiency.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances inview. It is one object of the present invention to provide a heat pipe,which eliminates fluid accumulation, thereby maintaining excellenttemperature uniformity.

To achieve this and other objects of the present invention, the heatpipe comprises a pipe body having two distal ends closed, a wickstructure formed on the inside wall of said pipe body and having apredetermined thickness, and a working fluid filled in the pipe body.The pipe body defines a heat absorbing section and a condensing section.The thickness of the wick structure in the heat absorbing section isgreater that the thickness of the wick structure in the condensingsection. By means of the design that the diameter of the spacesurrounded by the wick structure in the condensing section is greaterthan that in the heat absorbing section, the heat pipe eliminates fluidaccumulation and maintains excellent temperature uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top plain view of a heat pipe in accordance withthe present invention.

FIG. 2 is a schematic sectional view of the heat pipe in accordance withthe present invention.

FIG. 3 is an enlarged view of a part of FIG. 2.

FIG. 4 is a schematic sectional side view of a flattened heat pipeaccording to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-3, a heat pipe 10 in accordance with the presentinvention is shown comprised of a pipe body 11, a wick structure 21, anda working fluid 31. The pipe body 11 has its two distal ends closed. Thewick structure 21 is formed on the inside wall of the pipe body 11,having a predetermined thickness. The working fluid 31 is filled in thepipe body 11.

The pipe body 1 defines a heat absorbing section H, a heat isolationsection A, and a condensing section C. The thickness of the wickstructure 21 at the heat absorbing section H is greater than thethickness of the wick structure 21 at the condensing section C. The heatisolation section A is connected between the heat absorbing section Hand the condensing section C. The wick structure 21 at the heatisolation section A is relatively thicker at the end close to the heatabsorbing section H and relatively thinner at the end close to thecondensing section C. Further, the wick structure 21 at the heatisolation section A reduces gradually from the thicker end toward thethinner end, i.e., reduces gradually in direction from the heatabsorbing section H toward the condensing section C.

Referring to FIG. 2 again, when the heat pipe 10 is in use, the fluid 31inside the heat absorbing section H is heated into steam that flowsthrough the space surrounded by the wick structure 21 in the heatabsorbing section H to the heat isolation section A and then thecondensing section C. When reached the condensing section C, steam iscondensed into a fluid 31 that enters the wick structure 21. Because thewick structure 21 is relatively thinner at the condensing section C, thediameter of the space surrounded by the wick structure 21 inside thecondensing section C is relatively greater, the amount of the condensedfluid 31 in the condensing section C is insufficient to block the spacesurrounded by the wick structure 21 inside the condensing section C,therefore no fluid accumulation will occur. FIG. 3 illustrates the fluid31 condensed at the wick structure 21. Therefore, the wick structure 21quickly guides the condensed fluid 31 back to the heat absorbing sectionH for further circulation, maintaining excellent temperature uniformityand achieving excellent heat transfer effect.

As stated above, the wick structure 21 is relatively thicker at the heatabsorbing section H and relatively thinner at the condensing section C.In consequence, the diameter of the space surrounded by the wickstructure 21 at the heat absorbing section H is relatively smaller thanthe diameter of the space surrounded by the wick structure 21 at thecondensing section C. Therefore, the steam pressure in the heatabsorbing section H is greater than the steam pressure in the condensingsection C, facilitating movement of steam toward the condensing sectionC.

Therefore, the invention effectively eliminates the problems of fluidaccumulation and non-uniformity of temperature of the prior art design.By means of the wick thickness variation design, the invention preventsblocking of the space surrounded by the wick structure at the condensingsection, eliminating water accumulation and maintaining excellenttemperature uniformity.

1. A heat pipe comprising: a pipe body, said pipe having two distal endsclosed; a wick structure formed on the inside wall of said pipe body,said wick having a predetermined thickness; and a working fluid filledin said pipe body; wherein said pipe body defines a heat absorbingsection and a condensing section; the thickness of said wick structurein said heat absorbing section is greater that the thickness of saidwick structure in said condensing section.
 2. The heat pipe as claimedin claim 1, wherein said pipe body further defines a heat isolationsection connected between said heat absorbing section and saidcondensing section.
 3. The heat pipe as claimed in claim 2, wherein thethickness of said wick structure in said heat isolation section isrelatively thicker at one end and relatively thinner at an opposite end.4. The heat pipe as claimed in claim 3, wherein the relatively thickerend of the part of said wick structure in said heat isolation section isclose to said heat absorbing section and the relatively thinner end ofthe part of said wick structure in said heat isolation section is closeto said condensing section.
 5. The heat pipe as claimed in claim 3,wherein the thickness of said wick structure in said heat isolationsection gradually reduces in direction from said heat absorbing sectiontoward said condensing section.